The present invention relates generally to an apparatus and method for removing selected articles, such as cigarettes, from a conveyor pathway during manufacturing or processing operations.
In known cigarette manufacturing operations, cigarettes typically are processed and transported on processing drums. Cigarettes are positioned in flutes that are axially spaced along the periphery of the processing drums, which rotate about stationary valve members. The cigarettes are held in place in the flutes by vacuum suction conveyed to the flutes through conduits. These conduits extend radially inward from the flutes to a vacuum chamber. A vacuum generator provides the vacuum suction to the vacuum chamber through the stationary valve member. The force of the vacuum suction is sufficient to hold the cigarettes in position on the flutes, overcoming the combined forces on the cigarettes of gravity and the centrifugal force from the rotating conveyor.
Cigarettes are transferred from one processing drum to another at a transfer point, which generally is the point at which the two processing drums are closest together. At the transfer point a flute on one drum is adjacent to a flute on the other drum.
It is known to transfer cigarettes from one drum to another by a vacuum transfer system, such as that used in the MAX S filter tipping machine, which is manufactured by Hauni-Werke Korber & Co. KG, Hamburg, Germany. In such a vacuum transfer system, the vacuum suction applied to the flute on the transfer drum is blocked just as the flute reaches the transfer point. Centrifugal forces due to the transfer drum rotation and vacuum suction from the adjacent flute on the receiving drum combine to overcome the gravitational force and residual vacuum suction, if any, that remains in the flute on the transfer drum, thereby causing transfer to the receiving drum.
For quality control in cigarette manufacturing and processing, it is desirable to select and remove cigarettes from the processing drum transport pathway--either to eliminate defective cigarettes or for testing. One known scheme for selectively removing cigarettes is air-jet ejection.
In the air-jet ejection scheme, a defect detection device or other trigger-determining mechanism causes a signal to trigger an air-jet device to eject a selected cigarette from the processing drum. The air jet device shoots a high-pressure pulse of air (typically at 60-180 psi) through a conduit, which jettisons the selected cigarette off the flute.
It is a disadvantage of the air-jet scheme that the force of the air jet must be sufficiently strong to overcome the vacuum suction, but must be applied with a sufficiently short pulse such that the vacuum suction returns before the next flute rotates to the position adjacent to the air jet. It is a related disadvantage that frequent maintenance typically is required to use the air-jet scheme at the high speeds typical in modern cigarette processing machines.
It is a further disadvantage that a delicate balance is required to produce high pressure that quickly dissipates. This requires typically expensive triggering and timing devices.
It is another disadvantage of the air-jet scheme that the high pressure of the air stream required to overpower the vacuum suction can damage the selected cigarette, hampering the analysis of the cause of defects in the cigarette, or defeating quality control sampling.
It is yet another disadvantage of the air-jet scheme that cigarettes can be ejected in unpredictable trajectories, which can cause the selected cigarettes to miss the collecting receptacle.
Another known scheme for selectively removing cigarettes from processing drums is selective transfer blocking, such as taught in Brand U.S. Pat. No. 4,452,255, issued Jun. 5, 1984. In the selective transfer blocking scheme, acceptable cigarettes are transferred from one drum to another while transfer of defective cigarettes is blocked. Transfer is blocked by turning on a suction generator in the transferor drum inducing suction on the defective cigarette at the transfer point while simultaneously shooting a compressed air from the receiving drum in order to further reduce the likelihood of transfer of the defective cigarette. Transfer is accomplished by providing ambient air pressure to the cigarette to be transferred in the transferor drum while maintaining a suction force in the receiving drum.
The selective transfer blocking scheme has a disadvantage of requiring a pulse of high-pressure air to be split into two pipes--a pressure line that releases the air jet to the receiving flute and a pipe that simultaneously causes a vacuum to be pulled at the transfer flute.